Centrifugal fan



A. A. CRIQUI. CENTRIFUAGAL FAN. APPLICATION FILED SEPT. 11.1mm

Patented J 11116 1, 1920.

. JANET/7'01? A TTOEIYBY UNITED TAT ALBERT A. GRIQUI, OF BUFFALO, NEW

PATENT optics.

YORK, ASSIGNOR TO BUFFALO FORGE comrm, OEBUFFALO, NEW YORK, A CORPORATION or NEW YORK.

CENTRIFUGAL FAN.

Specification of Letters Patent. -Patented June 1, 1920,

Application filed September 7,1915. Serial No. 49,193.

certain new and useful Improvements in Centrifugal Fans, of which the following is a full, clear, and exact description.

My invention relates generally to 'a multiblade, centrifugal fan of thetype in which a large number of blades are arranged in' an annular series around a central space, open at one side for the entrance of the 2 air which is drawn in through the central opening and forced outwardly through the spaces between the blades by centrifugal force. 1

My invention relates generally to improvements in the formation of the blades which form part of the wheel ofa centrif-. ugal fan. The centrifugal fan of this application in some respects is similar to that .shown and described in my co-pending application. SerialNo. 174,384, which shows a fan wheel at a slow speed, which requires alarge frame motor in order that the slow speed may be maintained. This is because .of the fact that in most fan constructions, inventors-have sought to produce fans 1n ,which the velocity of the air leaving the wheel will be greater than theperipheral velocity of the wheel.

The general object of my invent on has been, therefore, to provide afan havinga wheel with blades in which the velocity of the .air leaving the wheel shall be. less than the velocity of the periphery of-the wheel, thereby'producing a low velocity pressure at a comparatively high speed of rotation.

; peripheral velocity.

Inmy fan, a snail-shaped casing is used, by means ofwhich a portion of the velocity pressure of the air leaving the wheel is converted into static pressure. My wheel will, therefore, produce a lower static pressure than a ,wheel having forwardly curved blades,'both wheels running at the same Another object. has been to provide a fan wheel having blades so formed that the friction of the air passing through the blades shall be greatly minimized and thus produce a fan having maximum efficiency.

Another object has been to provide a blade which shall equalize the air along the entire length of the same and also one which shall pick up the air at a minimum loss by shock or impact with the entering air.

Another object has'been to' provide a blade, the surfaces of which are formed from two truncated cones anda flat surface,

said flat surface lying in a plane which is.

tangent-to the surfaces of said cones. I

Another object has been to provide a blade that will make it possible to attain different air pressures with the same revolutions perminute with the Wheel by varying the radial dimension of the flat portion of the blade to suit the pressure requirements.

.Each blade of my fan, as described herein, has a forwardly curved heel and a backwardly, curved tip. By reason of the backward curve at the tip, the kinetic energy of the air, as it leaves the tip, is reduced to a minimum, thereby producing a static pressure resulting from the conversion of velocity which is far less than that produced by the inwardly curved .or straight surface type of blade.

Throughout this description, I have used the term air, but obviously, mydevice may .be advantageously used-with gas or other fluids, and it is not intended to restrict my invention to the use of air.

A structure somewhat similar-.to'that 'disclosed herein, is described in my Letters.

. I have. accomplished the above objects and advantages by the device shownin the accompanying drawings which form a part of this application. In the drawings, like characters of reference indicate like parts throughout the several figures, of which:

Figure 1 is a sectional, side elevation of a complete fan. Fig. 2 is an endelevation of a complete blade and shows diagrammatically the manner in which the blade is formed. Fig. 3 shows. aside elevation ofthe blade illustrated in Fig. 2.

Fig. 4 is an end elevation of a modified form of blade and shows, in a diagrammatical manner, a means of ascertaining the comparative pressures and velocities developed at each corner of the tip of the blade.

Fig. 5 is'a side elevation of the blade shown in Fig. 4. A v 4 Fig. 6 is an end elevation of the blade similar tothat shown in Fig. 2 and shows, in a 'diagrammatical manner, a means of ascertaining the comparative pressures and velocities developed at each corner.

Referring to the drawings, 10 represents the wheel of my fan which is carried by a shaft 11, mounted within a suitable bearing 12 and provided with any desired means of motive power (not shown.) The wheel 10 is inclosed within a snail-shaped casing 13 having an inlet opening oreye' 14 adjacent to the inlet of the wheel 10 and also with an inlet cone 15, which fits into the inlet eye 11 and directs the air from the exterior of the easing into the central opening of the wheel. The casing is also provided with the usual tangential opening which, for clearness of illustration, has not been shown. The'blad'es 16 are secured at one end to a disk 17 carried by a'hub 18, secured to the shaft 11. An annular band orring 19 v is arranged at the inlet end of the wheel and the outer ends of the blade 16 are secured to said ring by any suitable means.

In the ordinary type of fan, as is well known, the tendency of the entering air is to rush to the end farthest from the entrance and be discharged from that part of the wheel, thus making the discharge at the entrance end of the wheel comparatively slight. In order to produce a uniform discharge of air along the entire length of the blade, I have made the wheel 10 conical in shape, as shown in Fig. 1. It will be seen from this figure that the wheel is larger in diameter at the entrance end than at the disk end thereof. The blades 16 are also narrower at the entrance end of the wheel than they are at the disk end thereof. Owing to this difference of diameters of the wheel, the peripheral velocity of the tips .of the blades will be greater at the entrance end of the wheel than at the disk end, and thus force the greater amount of air through the blades at this oint, which tends to equalize the velocity 0 the air along the tip of the blade. It is sometimes desired to'make the wheels of substantially uniform diameter at each end, and in such cases blades of the type illustrated in Figs. 4 and 5 may be used. When wheels of-this type are used, the equalization of the air discharge at the tip of the blade above referred to, is accomplished by changing the curvature of the blade along the tip and. thus changing the an le at which the air leaves the same.

The blades of my fan are each formed from two cones and a flat surface, said fiat surface lying in the plane which is tangent to the surface of both cones. The blades are so formed that the concave surface of each is presented to the air at the heel of the blade and the convex surface is presented to the air as it leaves the tip of the blade. These blades may have their tips and heels coplanar or non-coplanar with the'axisof the wheel and, as required, may have the entrance end of the tip and heel preceding or following the disk end thereof, to suit different conditions.

Referring now to Fig. 2, it will be seen that the blade 20 is formed partly from the surfaces of two truncated cones A and B. These cones are arranged to have their surfaces tangent to a plane which passes the apex of the cone B is represented at b. I

The axis of the cone A is represented bg the line wa and the axis of the cone is represented by the linebb'. The tip 21 of the blade shown in Figs. 2 and 6 is coplanar with the axis 0 of the wheel and the heel 22 of the blade is-non-coplanar with the axis of the wheel. The end 21 of the tip of. the blade is farther from the axis in a-radial direction than the end 21 and the end 22 of the'heel of the blade is nearer the axis of the wheel in a radial direction than the end 22 and it precedes the end 22". From these figures, it will be clearly seen that the tip and heel portions of the blade are curved backwardly and forwardly, re-,

spectively, and that between them and tan.- gent to these curved surfaces is a. substangle 'to a radial line passing through the wheel. By varying the width of this fiat surface, that is the radial dimension of the fiat portion of the blade, the fan can be made to suit different pressure re uirements.

By increasing the width of this at surface I am' able to increase the static pressure pro duced by the fan, while maintaining a con- Referring now more particularly to Fig.

6, where I show, in a diagrammatlcal man- 1 the full line 22 -e. The lineal velocity of the blade at the end 22 of the heel is indicatedby the broken line 22"-0', and the radial velocity of the air through the blade at this end is indicated by the broken line' 22 .ol. The resultant velocity of the air at the end 22* of the heel of the blade is represented by the full line 22"e. The lineal velocity of the end 21 of the tipTff the blade is represented by the broken line 21 -C, which line is tangent to'the. e riphery ofthe wheel at the end-21 he blade at this end being curved backwardly, the air leaves the blade at a tangent to the outer curved surface of the same, and is rep-- resented by the broken line 21*- -D.' The resultant velocity of the air leaving the end 21 of the tip of the blade is indicated by the full line 21 E'. The lineal velocity ofthe air leaving the end 21 'of the tip is indicated by the tangential broken line 2l -C, and the line 21 D represents the tangential line of discharge of the air as it leaves this end of the tip of the blade. The resultant velocity of the air at the end 21 of the tip is indicated by the full line 2l"--E. It will beunderstood that the radial velocity of the air at the tip of the blade is indicated by the distance between the line indicating the lineal velocity of the tip of the blade and the line of the parallelogram which is parallel thereto. It will thus be seen that the resultant velocity of the air leaving the tipv of the blade is far less than the lineal velocity of the tip of the blade, thus giving a low resultant velocity pressure at a high speed of rotation.

Referring now to Figs. 4 and 5, where 1'. show a type of blade used in a-wheel of substantially equal diameter at each end, the

' blade-24L is develo ed from the two .truncated cones F and arranged to have a line along each of their surfaces tangent to a plane. passing through the fiat surface 25 which is formed on the blade between the twocurved surfaces. It will be seen that in this form of blade this. flat surface lies in a plane which is parallel to the axis of the wheel. The tip 26 of this blade lies in planes which are parallel and coplanar with a the axis of the wheel and the heel 27 is nonvi a.

ergy of the wheel at the end 26. The tip 0 the blade being curved backwardly, the air leaves the blade at a tangent tothe outer curved surface of the same and is represented by the broken line 26 D. The resultant velocity of the air leaving the end 26 of the tip of the blade is indlcated by the full line 26 --E. The end 26 of the tip ofthe blade'lies in a straight line with the end 26 when-the blade is viewed as shown in Fig. l and being behind the end 26 does not show in this figure. The tip of the blade is also parallel with the axis of the wheel so that the lineal velocity of the end 26* is the same .as' that of theend 26 and therefore it is represented by the same tangential broken line 26'C as is used to rep: resent the lineal velocity of'the end 26 of the blade. The broken line 26H represents the tangential line of discharge of-the air as it leaves this end of the tip of the blade. The resultant velocity of the air at the end 26 of the tip is indicated by the full line 26"J. i

As hereintofore pointed out, in order to equalize the velocity pressure at the tip in this form-of blade in which the curvature of the blade at. the tipis changed, it will 'be seen by reference to Fig. 4 that the angle formed between the line 26-'C, representing'the lineal velocity of the entrance end leaving the tip of the blade at that end, is

less than the angle formed between thelines 26" C and 26H at the disk end 26 .of the tip. The less the angle between the line representing the lineal velocity of the tip of theblade and the line representing the 'tangential discharge of air from the blade, the

it will clearly be seen, that the resultant velocity represented by the line 26"-J at the disk end of the blade is substantially equal line 26 -E at the entrance end of the blade 110,- to the resultant velocity represented by the whereby the velocity pressure at the tip of the blade is equalized.

. While i have shown and described my invention as applied to a fan havinga single wheel and a single inlet opening, it 1s obvious that it may be applied to-fans having a double opening or to fans having two wheels each provided with an inlet opening.

It is to be understood, that, while I have shown anddescribed the connecting surface as a fiat surface, still substantially the same a results may be obtained by the use of a con necting surface which is somewhat curved. This substantially fiat connection may also be used to vary the static pressure produced by a blade which is formed by the portion of. the surfaces of two cones and this connectingv surface but in a blade in which the tip hasa greater than a line included in a plane tangent to the surfaces of said cones.

2. A centrifugal fan having a wheel provided with a plurality of blades, a portion of the surface of each being formed from a portion of the surfaces of two cones, each of said blades having a forward and backward curve, and each having a portion of its surface greater than a line included in a plane tangent to the surfaces of said cones.

3. A centrifugal fan having'a wheel provided with a plurality of blades, a portion of the surface of each being formed from a portion of the surfaces of two cones and a portion of its surface greater than a line ineluded in-a plane tangent to the surfaces of said cones, each of said blades having a forward and backward curve, and the surface of'each of said blades which is presented to the air being concave at, its heel and convex at its tip,

4. A centrifugal fan having a wheel pros vided with a plurality of blades, a portion of the surface of each being formed from a portion of the surfaces of two cones, the tip of each blade bein substantially coplanar with .the axis of saif wheel, and each of said 40 blades having a portion of its surface greater than a line included in a plane tangent to the surfaces of said cones.

' the edge of the blade nearer t wheel havinga forward curve and the edge 5. A centrifugal fan having a wheelplo I vided with a plurality of blades, a portion a.

of the surface of each being formed from a portion of the surfaces of two cones, the

heel of each blade being non-coplanar with the axis of said wheel and each of said blades having a portion of its surface greater than a line included in a plane tangent to the surfaces of said cones.

6. A .centrifugal fan having a wheel provided with a plurality of blades, a portion of the surface of each being formed from a portion of the surfaces of two cones and a portion from aplane.

7 A centrifugal fan portion of the surfaces of two cones and a portion'from a plane, each of said cones having a surface tangent to said plane.

8. A centrifugal fan having a wheel provided with a plurality of blades, a portion of the; surface of each being formed from a-portlon of the surfaces of two cones, each having a wheel ,provided with a plurality of blades, a portion of the surface of each being formed from a of which is tangent 'to the connecting surface.

9. A centrifugal fan having a wheel provided with a plurality of blades, a portion of the surface of each being formed from portions of conical surfaces and a. portion thereof being formed from a lane surface,

he axis of the of the blade farther from the axis'having a backward curve. j I

In testimony whereof, I have hereunto signed my name in the presence of two subscribing .witnesses.

ALBERT A. CRIQUI.

Witnesses:

J. WM. ELLIs, WALTER H. KELLEY. 

